a. Field of the Invention
This invention relates to self-propelled hydraulic lifts of the type having an extensible boom terminating in a work platform.
b. Brief Description of the Prior Art
Self-propelled hydraulic lifts are well-known, as, for example, is shown in U.S. Pat. No. 3,319,739, issued May 16, 1967. Extensible and rotatable booms on devices of this general type are also well known as is shown, for example, in U.S. Pat. No. 2,786,723, issued Mar. 26, 1957. Extensible boom assemblies which provide for remote control of the boom at a workman's platform attached to the outer end of the boom are illustrated, for example, in U.S. Pat. No. 3,136,385, issued June 9, 1964 to J. M. Eitel and U.S. Pat. No. 3,379,279 issued Apr. 23, 1968 to E. G. Slusher.
However, such conventional lifts suffer from several disadvantages which limit their utility. For example, such lifts, conventionally, have either been mounted on a truck body, U.S. Pat. No. 3,136,385, for example, or have utilized a counterweight extending significantly beyond the point of attachment of the boom to the lift. In either event, the resulting structure is relatively large, limiting its access and/or rotation to comparatively wide passageways. Furthermore, when an extensible boom has been used, control cables necessarily included within the boom for remote control of the lift have been subject to wear and failure by reason of the repeated stresses applied thereto during boom extension and retraction.